January, 2007
Alternative Tree Crops Information Series No. 6
University of Idaho College of Natural Resources
Oaks
Yvonne C. Barkley
Long-lived and majestic,
oaks (Quercus spp.) have
been venerated and
worshipped by the ancient
people of both Old and
New worlds. Oaks form a
large genus of about 500
species of trees and
shrubs, with 58 species of oaks native to the United
States and Canada.
Owing to their impermeability to liquids, strength, and
durability, wood from the white oak group is favored
for wine barrels. The wood from all oaks is prized for
its hardness, resistance to abrasion, smooth finishing
qualities, and good nail holding capacities. Oak is used
to make beautiful furniture, cabinets, and flooring. Red
and gray squirrels, white-tail deer, wood ducks, wild
turkey, and a variety of woodpeckers, jays, and
nuthatches all benefit greatly from the food provided
by oaks.
Biology and Silvics
Oaks are widely distributed throughout the temperate
regions of the northern hemisphere and at higher
elevations in the tropical climates of Columbia, North
Africa, and Indonesia. In the United States, oaks are
found in a wide variety of habitats and climates. Form
and size varies, from scrubby species that reach 20
feet in height and live a mere 200 years to grand,
stately species that can reach 100+ feet in height and
live 400 to 500 years.
The Quercus genus is divided into two groups. The
white oak group includes: true white oaks, such as
white oak (Q. alba) and bur oak (Q. macrocarpa):
chestnut oaks, such as swamp chestnut oak (Q.
michauxii) and chinkapin oak (Q. muehlenbergii);
and live oaks, such as live oak (Q. viginiana) and
blue oak (Q. douglasii). This group has leaves that
lack a spiny tip and acorns with sweet seeds and
thick, scaly cups that mature in one year. Acorns of the
white oak group germinate in fall, which often presents
a problem in northern regions where the ground
freezes before young emerging roots can become
established.
The red and black oak group includes: true red and
black oaks such as northern red oak (Q. rubra),
scarlet oak (Q. coccinea), and pin oak (Q. palustris);
willow oak (Q. phellos); laurel oak (Q.
hemisphaerica); water oak (Q. nigra); and western
live oaks such as interior live oak (Q. wislizeni) and
coast live oak (Q. agrifolia). This group has leaves
with spiny tips or lobes and acorns with bitter seeds
and thin cup scales. Acorns in this group mature at the
end of two growing seasons and are borne on the
previous year’s branches. Germination does not take
place until the spring following seed fall and many
acorns can be destroyed by insects.
Oaks in general are deep-rooted and at the end of the
first growing season can have three to four inches of
slender top growth with a ¼ - ½ inch diameter taproot
that extends a foot or more into the ground. Most
species of oaks are classed as intermediate to intolerant of shade, and have the ability to complete multiple
cycles of growth, meaning that tops can decline and
die back while roots remain alive and increase in size
and stored energy. Oaks are prolific stump sprouters
and sprouts can respond favorably to release, producing trees of excellent form and quality. Oaks readily
hybridize and, in mixed stands, are sometimes difficult
to tell apart. Recognized as either white oak or red
oak in the lumber industry, each type includes wood of
a number of species from each group.
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IDAHO FOREST, WILDLIFEAND RANGE EXPERIMENT STATION
DIRECTOR - STEVE B. DALEY LAURSEN
Establishment
At a glance …
White oak group
Site selection. Although oaks grow in a wide range of
soils and climates, all species will do well on sites with
deep, well-drained soils with pH values between 5.5
and 7.0. Overall, oaks tend to be fairly droughttolerant. In Idaho, they will do best on gentle north- to
east-facing slopes or flat, well-drained bottomlands,
though species such as swamp white oak and pin oak
will tolerate poorly drained soils. Oaks leaf out later
than other hardwood species and because of this
escape all but the latest of spring frosts.
Species: Quercus alba
Common names: white oak, stave oak.
Native range: eastern United States.
Hardiness: USDA Zone 3 to 9.
Soil type: wide variety of soils and sites; will
tolerate dry soils, mildly alkaline pH, and
moderate soil compaction; growth good on all
but rocky, wet, or poorly-drained sites.
Shade tolerance: intolerant.
Form: large, semi-formal tree; 50 to 80 feet tall.
Regional insect & disease problems: oak wilt;
anthracnose.
Objectionable characteristics: difficult to
transplant.
Other: nuts provide mast for wildlife; wood very
valuable, used for furniture and barrels.
Planting densities. Oak plantations can be planted at
eight by 14 foot spacing. We have found that planting
oak closer together within the rows encourages a
straighter form, development of a single leader, and
less basal and bole sprouting than more generous
spacings.
Planting stock. As oaks have such a wide native
range and readily hybridize, it is important to purchase
trees from known seed sources. Seedlings from more
northern seed sources are preferred for Idaho.
Species: Quercus bicolor
Common names: swamp white oak.
Native range: northeastern United States; found
in both upland and wet areas subject to
flooding, though not in areas permanently
under water.
Hardiness: USDA Zone 3 to 8.
Soil type: tolerates poorly drained soils.
Shade tolerance: intermediate.
Form: long-lived, medium-sized tree; 50 to 70 feet
tall with an irregular, open crown.
Regional insect & disease problems: anthracnose, oak wilt.
Objectionable characteristics: does not tolerate
extended drought.
Other: wood similar to white oak in character and
value; acorns provide food for wildlife; good
species for low-lying areas subject to standing
water or flooding.
Culture and Management
Pruning. Oaks are prolific sprouters and sprouts are
easiest to remove as they are emerging in the spring by
rubbing them off with your gloved hand. Experience
has shown that not only is this the most efficient way to
remove multiple sprouts, but it also seems to inhibit
subsequent sprouting for the rest of that growing
season. Continued removal of sprouts, as well as
limbing up branches annually, will ensure future log
quality.
Thinning. As trees mature, a commercial thinning can
take place at approximately year 20. Every other tree
can be removed to open the plantation up to a 16 by
14 foot spacing. Trees taken can be used for specialty
products such as turned bowls and vases, spoons,
furniture, and flooring. The remaining trees can then be
left to grow into larger, veneer quality logs.
Species: Quercus gambelii
Common names: Gambel’s oak, Rocky Mountain
white oak.
Native range: central Rocky Mountains.
Hardiness: USDA Zone 2 to 8.
Soil type: wide variety of soils and sites; on dry
Excellent wood qualities, adaptability to a wide range
of growing conditions, superb wildlife value, and vivid
fall coloration all make the Quercus species attractive
selections for alternative tree crops for Idaho.
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fairly short trunk.
Regional insect and disease problems: oak
wilt.
Objectional characteristics: some seed sources
have poor form when young.
Other: many English ships have been constructed
from English oak, as were countless interiors
of castles and churches; the preferred wood
for wine barrels.
foothills, canyons, and lower slopes from 5,000
to 9,000 foot elevation.
Shade tolerance: intermediate.
Form: multi-stemmed trunk reaching 15 to 30 feet
in height; rounded crown; often forms thickets.
Regional insect and disease problems: no
serious threats.
Objectional characteristics: none.
Other: wood is hard, heavy, and close grained,
though not often used commercially it is used
locally for firewood. One of the most drought
tolerant of the oaks.
Red\black oak group
Species: Quercus coccinea
Common names: scarlet, black, red, Spanish oak.
Native range: eastern United States, from
southwestern Maine west to southern Michigan and south to central Mississippi; found up
to 5,000 foot elevation in Appalachian Mountains; native range within humid region.
Hardiness: USDA Zone 4 to 9.
Soil type: on dry, sandy sites; will tolerate a wide
variety of soils; low to moderate moisture
requirements.
Shade tolerance: very intolerant.
Form: medium-sized tree; 60 to 80 feet tall with
an open, rounded crown.
Regional insect & disease problems: oak wilt,
cankers, tent caterpillar.
Objectionable characteristics: susceptible to
fire damage, sunscald.
Other: lumber mixed and sold with other red oak
species.
Species: Quercus macrocarpa
Common names: bur oak, mossycup oak, mossyovercup oak, and scrub oak.
Native range: eastern North America, with
extensions into south-central United States,
where it is a pioneer species and frequently
planted in windbreaks.
Hardiness: USDA Zone 2 to 8.
Soil type: from moist bottomlands to dry hillsides,
mainly in limestone soils.
Shade tolerance: intermediate.
Form: medium to tall tree; 65 to 130 feet tall, with
a broad, spreading crown.
Regional insect & disease problems: oak wilt.
Objectional characteristics: will not tolerate
flooding.
Other: resistant to injury by fire; very drought
resistant; large seed crops produced every
two to three years offer excellent food
supplies to a wide variety of wildlife; wood is
very hard, heavy, strong, and durable - usually
marketed as white oak.
Species: Quercus palustris
Common names: pin oak, swamp oak, water oak,
and swamp Spanish oak.
Native range: middle Atlantic and central United
States.
Hardimess: USDA Zone 4 to 8.
Soil type: primarily a low-land tree that thrives in
poorly drained, claypan soils typical of floodplains; grows well in deep, well-drained soils;
becomes chlorotic in alkaline soils.
Shade tolerance: intolerant.
Form: fast-growing, short-lived, medium sized
Species: Quercus robur
Common names: English oak.
Native range: England; escaped widely in the
United States.
Hardiness: USDA Zone 4 to 8.
Soil type: thrives in clays soils, but adapts well to
lighter, stonier soils.
Shade tolerance: intermediate.
Form: large tree; 150 feet tall or more, with a
wide-spreading crown rising from a sturdy,
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tree; 50 to 80 feet tall with a broad, pyramid
shaped crown.
Regional insect & disease problems: oak wilt.
Objectional characteristics: iron chlorosis in
alkaline soils.
Other: transplants well; tolerates short periods of
flooding; good for use in areas too wet to
support other species; large acorn crops every
two to three years valuable for wildlife, especially ducks; wood is coarse-grained, hard,
heavy, and is used in general construction as
posts and for firewood; an ornamental favorite;
one of the best oaks for fall color.
Species: Quercus rubra
Common names: northern red oak, eastern red
oak, mountain red oak, gray oak.
Native range: eastern United States; only native
red oak extending into Nova Scotia.
Hardiness: USDA Zone 4 to 8.
Soil type: will tolerate moist or dry soils; does well
in alkaline conditions, with moderate irrigation.
Shade tolerance: intolerant.
Form: large, semi-formal tree; 60 to 90 feet tall
with a spread of 40 to 60 feet.
Regional insect & disease problems: oak wilt.
Objectionable characteristics: susceptible to
damage from fire.
Other: less difficult to transplant than most oaks;
tolerates air pollution, compacted soils; hardy
throughout Idaho; nuts provide important food
for squirrels, turkeys, mice, and other mammals
and birds.
About the Author: Yvonne C. Barkley is an Associate Extension Forester with University of Idaho Extension.
Graphic artist: Lorraine Ashland.
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